A large number of prior art shoulder height adjustment mechanisms are available and have been described in various patents for adjusting the incremental height and location of the shoulder belt which is usually mounted to a turning loop or D-ring affixed to the height adjuster to accommodate the various positions that different sizes of occupants of a vehicle desire for the seat belt to be anatomically, correctly positioned for best results. Usually the belt passes through the swivel D-ring which may be freely pivotal about the axis of a bolt which is connected to a slider of the height adjuster. The vehicle passenger will adjust the height of the slider along an internal guide rail which usually has a series of openings spaced at different heights into which a portion of the slider or other mechanism is positioned to lock the slider and thereby the swivel D-ring at the desired height. From a mechanical standpoint the height adjuster must be sufficiently strong to withstand the loads which are encountered during a vehicle accident.
Many of the prior art height adjusters have had a number of parts or complex parts which are expensive to manufacture and to assemble for use in the height adjuster. Particularly there is a spring which biases the slider to a locking position in which portions such as locking protrusions or lugs on the slider fit into the openings or holes formed in the guide rail until such time as there is a need for height adjustment. For height adjustments, the vehicle occupant typically will operate an actuator button or press the slider or D-ring itself to compress the spring and to remove the locking protrusions from the locking position in the rail so that the slider may be shifted vertically along the rail. When the force compressing the spring is released, the protrusions are again fitted into locking openings in the rail to thereby lock the height adjuster in the newly adjusted position that is desired by the user. From a vehicle occupant standpoint, it is preferred that the height adjuster be easy to use and be readily apparent as to how it is to be used without the user having to consult an owner's manual or the like. Because of the varying capabilities of the passengers, it is preferred that the height adjuster require only a low force operation and yet still have a good, secure locking condition of the slider relative to the rail. From the manufacturing standpoint, it is particularly desirable to reduce the part count and the complexity of the parts so as to provide a relatively inexpensive height adjuster which is still easy to use and can be operated with a relatively low force.
There is prior art that purports to disclose height adjusters of relatively simple design such as in U.S. Pat. No. 4,180,023, but in that instance the slider body comprises an upper portion or part and a lower portion or part which are welded together to form the slider. The welding operation and the joining of two separate parts defeats the goal of lowering costs resulting in a high cost part from a manufacturing perspective. U.S. Pat. No. 5,044,666 discloses a height adjust mechanism with a very complex leaf spring element which extends essentially over the length and the width of the slider and is connected with the slider to form a clamping module along the rail. This large leaf spring and slider adjustment element are connected by a protruding portion on the slidable adjustment element extending through a slot in the spring. Further, the guide bar of the '666 patent has a large, central longitudinally extending slot through which portions of the clamping module extend. The large slot can make the flat guide bar weaker than is desired. To this end, the '666 patent also teaches more complexly configured and thus costly guide bars such as with thick, longitudinal upstanding edge walls or a C-shaped channel guide bar.